I have seen some very knowledgeable posts concerning steam engines.
Many of them talk about “SUPERPOWER”. While I have a vague understanding of the term, I thought it might be useful to define:
The boiler conditions & size; 2) the Piston sizes; 3) the driver sizes; 4) the tractive effort; 5) the time frame of introduction; & 6) any other criteria that separate Superpower from the earlier locomotives.
If one were to apply the term to diesel-electric locomotives, what other types of questions might arise…?
Lima started using the term in the mid 1920’s. They had 4-wheel trailing trucks to help support a firebox large enough to produce enough steam for high speed operation. Remember, this was the era of drag freights.
[quote user=“JC UPTON”]
“SUPERPOWER” – while I have a vague understanding of the term, I thought it might be useful to define:
The boiler conditions & size; 2) the Piston sizes; 3) the driver sizes; 4) the tractive effort; 5) the time frame of introduction; & 6) any other criteria that separate Superpower from the earlier locomotives.
Of these, only 1 and 5 really apply. Super-Power really originated with Lima, in 1925, with the A-1 design that evolved out of the NYC Mikado #8000 design. The point is to have a combination of boiler capacity and running gear that can make full horsepower at higher speed, with a critical part of this involving evaporation and another critical part involving superheat. Since more superheat involves more flues replacing tubes in the convection section, the design requires more radiant heating surface in the firebox and combustion chamber – which, with better circulation via syphons and arch tubes, and the heavier construction entirely behind the last driver pair, leads to the use of two-axle trucks (or bigger) for appropriate weight distribution and guiding.
The locomotive itself ahead of the rear tubesheet is not that different from a good Mikado design, and the weight on drivers, the ‘swept volume’ in the cylinders, and other details may not be very different. Something of a blind alley comes with large increases in boiler pressure, as this makes operation at lower speed with desired limited or short cutoff extremely peaky (i.e. more slip-prone) especially with more of th
The term has no meaning now, and it was never intended to have any specific meaning. It was just Lima’s marketing in 1925, trying to interest RRs in 2-8-4s and suchlike. The word caught on with railfans, who have used it ever since to describe big engines, of any sort (except maybe electric).
Lima claimed that RRs would be better off hauling tonnage trains with 2-8-4s rather than 2-8-2s or 2-10-2s – a train with a given tonnage could get over the road faster. That’s all Lima meant by Superpower – better speed, due to more power, allegedly with the same tonnage. Nothing to do with cylinder size or driver diameter or anything specific.
Will Woodard would, I think, disagree with you on some of the important points distinguishing the A 1 and later approaches, and so would the designers of the Allegheny who so rejoiced when their horsepower curves came back ‘better’ than the original one for the N&W A (and who shoehorned heavy efficiency-making piping into the design to the extent they had to lie about the weight to the unions…) I can say for a fact you’d have gotten some volubility out of Livio Dante Porta…
Super-Power has nothing whatsoever to do with “big” engines – there are aspects of the improvements in the GELSA metre-gauge locomotives, for example, and in the Norfolk Southern vest-pocket Berkshires. It does have to do with improvements that make better horsepower at speed – and at least one of those does, in fact, involve cylinders, albeit dimensions: the idea that even with the increased nominal augment found in taking stroke up to 34", reducing piston and rod dimensions to keep the desired swept volume, and better applicability of long-lap, long-travel valve action, could produce faster and better locomotives.
It could be equally argued that the late-Forties enhancements Townsend and Lima were touting were ‘marketing’ rather than actual thermodynamic and performance enhancements – for example, the combination of double-Belpaire with better defined radiant circulation that meant holding driver diameter to 76" or below; the use of improved Franklin type C valve gear of a number of types of drive; the implementation of Snyder preheaters and (presumably, eventually reliable) combined Turbo-Inspirators rather than heavy combinations of auxiliaries doing the same things – but it would be hard to say that the combination of those elements didn’t define a particular Lima philosophy. And that is what Super-Power means to steam designers, perhaps a
I’m just throwing this out there because I don’t want to start another thread on the subject (we’ve had too many already). This sorta concerns Super Power. Maybe the reason the PRR T1 wasn’t a success was that the people designing it didn’t know what they were doing? Think about it…the Pennsy hadn’t designed a running steam locomotive in close to 20 years-the M1. Many of the engineers involved in that, at least the senior ones, were probably retired. Baldwin was subjectively behind Lima and Alco in cutting edge designs. Also, with their continual financial problems, they probably couldn’t pay enough to keep any up-and-coming engineer from jumping ship. So, you had two companies that were the largest in their fields, but both of which had fallen behind in the times, trying to design a cutting-edge locomotive. Ain’t gonna happen. I expect to be flamed…
No flame here, but I don’t see incompetence, certainly not on the scale involving Baldwin and the ACL R-1 design. Part of the problem was with the folks at PRR being just a little, shall we say, overtrusting in what they needed in a high-speed design. Baldwin did try to tell them not to bet the farm on OC Franklin gear, and to design the firebox for 4-8-4 capability rather than assume ‘perfect passenger gas coal’ with the full economy in steam mass flow per dbhp that was supposedly coming from the duplex arrangement (before we start castigating PRR remember that Kiefer with the C1a made just the same estimation, involving the kind of accurate conventional valve gear and valves that Baldwin would likely have recommended). PRR had meanwhile spent what may have been an ungodly amount with Baldwin in particular but also Alco and Lima underwriting fundamental development on the S1 passenger engine – a very different and objectively “better” thing than the B&O and ATSF designs and the wacko '5/4 M1&#
Anyway, and as far as I can tell, superpower generically refers to putting 4-wheel trailing trucks on steam locomotives starting, I guess, in the mid 1920s, and Superpower specifically is a brand name from Lima of their Will Woodard-designed locomotives starting with their 2-8-4 Berkshire type.
ALCo (Upstate New York) and Baldwin (Philadelphia-based) were the big builders and Lima was the upstart from, Lima, Ohio that got its start building Shay geared locomotives and was trying to break into the big locomotive market.
The first Superpower product was the A1 2-8-4 Berkshire, where the formula included a lot of features, many new, some exotic and others catching on. These include the 4-wheel trailing truck to accomodate a large firebox, and many of the the 4-wheeled types that followed – 4-6-4 Hudson, and 4-8-4 Northern were small-s superpower. Other features included a booster engine driving one axle of the trailing truck to use the larger boiler capacity for this steam-hungry long-cutoff geared steam engine, a truncated frame where the trailing truck carried the tractive effort to the tender, a largish ashpan that moved with this “articulated” trailing truck, and outside steam pipe from the dome running above the boiler, which I guess was to be higher up and get drier steam, a large superheater, and that 60% limited cutoff for steam economy on heavy pulls at the expense of more wheel slip along with the long cutoff steam-heavy booster that was to mitigate that on starting.
The 4-wheel trailing truck and the bigger grate and superheater were perhaps the only innovations to catch on, with the “articulated trailing truck” and floating ashpan being replaced by a more conventional arrangement, the outside steam pipe not going anywhere outside Soviet Russia or China, the booster being viewed skeptically on a cost-of-maintenance/benefit basis, and the 60% limited cutoff being regarded as an engine-slipping gimmick?
Overmod, this V1 your keep talking about, what would have been the Whyte classification, and Bowes drive or no Bowes drive, how would it get power to the wheels? With the Big Gear and quill drive to the inner pairs of drivers carried by siderods to the outer pairs? By Cardan shafts like on the KM “America Lok” diesel hydraulics?
The V1 wheel arrangement was a bit weird: it used articulated cast underframes like a contemporary electric or the Baldwin Essl locomotive, but arranged strangely and unidirectionally, with the Q2-derived boiler’s firebox between the sets of drive axles, a bit Meyer-like, over a bearer truck.
PRR used a weird (and not very helpful) Whyte designation of 4-8-4-8 for this: a better way to typify it might be 4-8-0+4-8-0 but you still need to be looking at the chassis for that to make full sense. It used two 4000hp steam turbines, each driving four axles in the adjacent underframe via Cardan shaft – these were relatively low wheels and I don’t remember if flexible connections or ‘flexible gears’ were used in the drive as designed originally. The boiler faced backward over the rear frame, with the cab space at the backhead and the coal bunker ahead of that (as ‘stolen’ by Baldwin for the C&O M-1 layout; there is some amusing discussion in the surviving motive-power records at the Hagley regarding the ‘secret’ Baldwin project to ‘scoop’ PRR on making a large passenger turbine). Water – and for 8000hp from atmospheric-exhausting turbines it would be a lot – was from a separate water tender: strangely there didn’t seem to be any real effort to use multiple such tanks even though production of the original V1 prototype was abandoned after the war primarily on water-rate considerations.
I did not see any indication in the surviving technical documentation of any attempt to put a planetary transmission between the turbines and final drives in the original, slthough Westinghouse went to the trouble of patenting a two-speed version for a PRR S2-style locomotive, recognizing the issues with slip, tip losses etc. at low rotational speed. This is something that the Bowes drive would definitively fix, along with turbine overspeed at higher road mph – reading a bit between the lines this is where the fancy “passenger” shroud des
In the “drag freight” era, the first decade or two of the 20th century, steam engines were not very large and freight engines needed small drivers to help them pull long trains - kinda like a truck using a low gear going uphill. Railroads found they could use like a 2-10-2 instead of two 2-6-0s doubleheaded on a long mainline freight…but the 2-10-2 might only have 50-some inch drivers so could only go around 20 MPH.
With development of the large firebox made possible by the four-wheel trailing trucks, engines could be built much larger and with more power. This meant you could now build an engine like a 2-10-4 instead of a 2-10-2, but with 10-15" larger drivers. This meant the new engine could still haul a long train like the old one, but at much higher speeds than possible before with low-drivered engines.
GE, Westinghouse and others were promoting tying together the electric power utilities in the Northeast to make a “Superpower” system ca 1921. This was in response to a post WW1 fuel shortage, the grid would allow generation by larger and more efficient power plants.
I suspect Lima picked that up for marketing their locomotive design philosophy.
Steins liked to call it a 4-8-4-8 (which always bothered me) and an ‘effective’ Whyte representation can get into semantics. Perhaps the easiest way to visualize what the chassis resembled externally is to take a Baldwin Centipede chassis apart at the center articulation and turn the ‘back half’ around so the two pieces are connected elephant-style.
Although the pirated design for the C&O M-1 came about a decade later than the V1, we can use those locomotives for comparison as they had somewhat similar … as you might expect from a ‘Concordeski’ secret design crib … arrangement.
Each of the two chassis had its own Westinghouse turbine, of about 4000shp, located longitudinally. The coal bunker was in the nose; the modified Q2 boiler faced backward with the firebox over the second unit’s four-wheel ‘lead’ truck, with the cab at the backhead so conventional stoker arrangement could be used. All water was carried in a separate ‘water tender’, which on the design approved for production was not ‘bidirectional’. There was no trailing truck.
More like the second. As far as I know there was no clutch on the original to allow the turbines to be spooled to warm them, and I have not been able to find the reversing arrangement. The drive shows as Cardan shafts to right-angle gearboxes; I believe the wheels were a comparatively low 40".
The great point of the Bowes drive was that it constituted an electrical under/overdrive with no contact even with considerable axial displacement betw
Quote “Lima and PRR said limited cutoff gave a smoother torque curve. Why do you think they were wrong?”
They weren’t - it’s correct! Around 50 % you get the smallest jumps in a circular t.e. diagram of a two-cylinder engine, and it could and should be accompanied with a minimum of lead intake at that stage of running (this automatically means you have to provide for a variable advance because you want a larger lead at increasing speed.
I was given the opportunity to make some small tests myself when I visited (German) locomotives in Poland in 1990 / 91 / 92 (93). At Wolsztyn two crews let me drive their engine. I had coaxed them by doing some firing first - they liked that for obvious reasons, I didn’t care because it got me what I wanted to get. So on several tours, I mostly drove some 52s (PKP Ty-2/42) and the one 42 (Ty-3). Generally we had stopper trains that called at every station - so lots of opportunity to start away. Only once I was so lucky as to be on the footplate when a 52 had to step in for an Ol49 Prairie on a semi-fast out of Poznan on the mainline and we had to accelerate quickly and go full speed all the way. The engine had plenty of play in bearings, but she ran straight ahead, no nosing, only the coal wandered forward on the fire - but she did the job without complaint!
Usually, I started a train at ~65% and as soon as the engine turned wheels I linked in to 50 … 45 % and opened up wider. No engine ever slipped (although there was one incident that had an alarming moment to it - later!). With the 42 that was in quite good mechanical condition, I once even linked in to 40 % and opened up fully, keeping the large lever tightly gripped in expectation of a possible hefty slip - after the first “hushshh” she leaned in and I felt a slight pull back, there came the first loud beat “WHOOM!!” and then continued “Whoom! – Whoom! - Whoom! Whoom! Whoom whom whom …” - no slip, just a strong start! The driver sus